The safety feature can notify pilots of problems early in a flight, and possibly could have prevented the crash of Ethiopian Airlines flight 302 in March, Chris Brady, the author of Boeing’s 737 Technical Guide, told the BBC.

“I'm fairly confident that the Ethiopian Airlines flight probably would not have crashed if they had had the AOA disagree alert,” Brady said, referring to the safety software.

The crash, which killed all 157 passengers, is now being investigated, but the prime suspect is the malfunction of the aircraft’s flight control system. A doomed Lion Air flight out of Indonesia, also a 737 MAX, is said to have experienced a similar problem last October before it crashed, killing the 189 people onboard.

Boeing said last month that the alert, which could have prompted pilots to follow a different emergency procedure, “has not been considered a safety feature on airplanes and is not necessary for the safe operation of the airplane.”

The US Federal Aviation Administration concluded in an internal investigation earlier this month that the agency failed to properly oversee Boeing’s safety tests for the 737 MAX, deferring to the company’s own experts and allowing the defective systems through the agency’s approval process.